1. Field of the Invention
The present invention relates to a method for manufacturing an ink jet head in which droplets of conductive ink are expelled on a sheet of paper by causing vaporization of a portion of conductive ink due to an electric current flowing through the conductive ink.
2. Description of the Related Art
A printer utilized with a personal computer or a facsimile system has recently become popular for personal use while a large number of electronic devices have been utilized in an office. In this case, an ink jet printer has attracted a great deal of attention because the ink jet printer operates at a low noise level and high speed compared to impact printers. Especially, an on-demand type of ink jet printer is often utilized because the on-demand type of ink jet printer has a simple mechanism and is manufactured at a moderate price. In addition, droplets of ink are expelled on a sheet of paper on demanding in the on-demand type of ink jet printer so that the printer operates economically.
To expel the droplets of ink in the on-demand type of ink jet printer, many types of expelling methods have been proposed to date. For example, a portion of ink is mechanically pressurized and expelled by the action of a piezo-electric device in the ink jet printers disclosed in Japanese Patent Application Publication No. 2619/84 (S59-2619) and Japanese Patent Publication No. 38110/83 (S58-38110). Also, a portion of ink is pressurized by vaporizing the ink with an electrical resistive heater element in the ink jet printers disclosed in Japanese Patent Application Publication No. 59911/86 (S61-5991) and Japanese Patent Application Publication No. 54547/88 (S63-54547). In addition, a portion of conductive ink is vaporized by directly heating the conductive ink while passing an electric current through the conductive ink in the ink jet printer disclosed in U.S. Pat. No. 3,179,042. Furthermore, a portion of conductive ink is pressurized by vaporizing the conductive ink with an electric current in the ink jet printer disclosed in U.S. Pat. No. 4,595,938.
The ink jet printers of Japanese Patent Application Publication Nos. 2619/84 and 38110/83 are respectively provided with a piezo-electric device. Therefore, these ink jet printers respectively have a complicated mechanism and are expensive. In the same manner, because the ink jet printers of Japanese Patent Application Publication Nos. 59911/86 and 54547/88 are respectively provided with a heater element, the ink jet printers are inappropriate for commercial use.
On the other hand, the ink jet printers operated according to a direct electric heating method such as disclosed in U.S. Pat. Nos. 3,179,042 and 4,595,938 are appropriate for commercial use because only a pair of electrodes facing each other across a nozzle is required to vaporize the conductive ink. Accordingly, these ink jet printers can be manufactured with a simple structure even though they require a container for the conductive ink, a passageway for transmitting the conductive ink, a vaporizing system for vaporizing the conductive ink transmitted through the passageway, and an expelling system for expelling droplets of conductive ink.